1. Field of the Invention
The present invention relates to an image recording apparatus, an image recording method, an image processing apparatus, and a storage medium.
2. Description of the Related Art
Image recording apparatuses with which an image is formed on a recording medium by repeatedly performing print scanning and sub scanning have been known. In the print scanning, ink is discharged while the recording medium is scanned with a recording head in which a plurality of discharge ports for discharging ink are arranged. In the sub scanning, the recording medium is conveyed. In such image recording apparatuses, a so-called multipass method in which print scanning is performed in a unit region of the recording medium multiple times is generally employed.
In recent years, various inks and recording media have been used in such image recording apparatuses. A combination of an ink containing a pigment and a recording medium having low ink permeability is known for the purpose of forming an image with high brightness.
However, it is known that, when an image is recorded using the above-described ink and recording medium, the scratch resistance degrades because the image is recorded by fixing the ink on a surface of the recording medium. Japanese Patent Laid-Open No. 2000-272220 discloses that the scratch resistance is improved by adding a polymer having reactivity with a reaction liquid to an ink and causing the reaction liquid to react with the polymer in the ink on a surface of the recording medium. Japanese Patent Laid-Open No. 2000-272220 also discloses that use of a polymer having a film forming property improves the scratch resistance because a polymer film is formed on a surface of the ink fixed on the recording medium through the reaction with the reaction liquid.
However, the technique disclosed in Japanese Patent Laid-Open No. 2000-272220 requires a mechanism for applying the reaction liquid onto the recording medium, in addition to a mechanism for applying the ink. This may increase the cost.
As a result of studies conducted by the inventors of the present invention, it has been found that, when an ink containing a pigment is used, the scratch resistance is sometimes not sufficiently achieved because of a mechanism that has not been assumed. It has also been found that such degradation of the scratch resistance because of the mechanism particularly occurs when, for example, an ink containing an anionic coloring material or a polymer is used. This problem will be described below in detail.
FIGS. 1A to 1C show a process for fixing ink droplets 50 formed when an ink containing a pigment is discharged onto a recording medium 3 having low ink permeability.
FIG. 1A shows the state of ink applied onto the surface of the recording medium 3. A pigment ink is fixed through vaporization of volatile components such as water contained in the ink. In particular, when an ink having an anionic group is used, an acid-precipitation reaction may occur in the ink droplets 50 that have been applied onto the recording medium 3. An acid-precipitation reaction is a reaction described below. When a pigment stably dispersed in ink due to electrostatic repulsion between acid dissociation anionic groups (e.g., —COO−) of a polymer dispersant contacts an acid liquid composition or a recording medium, the acid dissociation anionic groups of the polymer dispersant are changed into non-dissociation anionic groups (e.g., —COOH) and the electrostatic repulsion is lost. As a result, the dispersion state of the pigment is disturbed and the pigment precipitates as an ink film 51.
FIG. 1B shows the state of ink on which an ink film 51 has been formed after the state in FIG. 1A. Since the ink film 51 is formed on each of the surfaces of the ink droplets 50 by the above-described acid-precipitation reaction, the vaporization of volatile components left in the ink droplets 50 is suppressed.
FIG. 1C shows the state of ink after the image recording has been completed. As a result of the acid-precipitation reaction, ink dots are stacked while volatile components are left in the ink droplets 50 even after the recording. Such a region in which the volatile components are left after the recording does not serve as an ink layer having sufficient fastness. If the region is rubbed with paper, cloth, or the like, the recorded image may be detached from the recording medium and the region may serve as a starting point of the detachment.